Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a first embodiment of a display screen or portion thereof with transitional graphical user interface showing a first image in a sequence, showing my new design;

FIG. 2 is a front view showing a second image thereof;

FIG. 3 is a front view showing a third image thereof;

FIG. 4 is a front view of a second embodiment of a display screen or portion thereof with transitional graphical user interface showing a first image in a sequence, showing my new design;

FIG. 5 is a front view showing a second image thereof; and,

FIG. 6 is a front view showing a third image thereof.

The outermost perimeter illustrated by a pair of dashed broken lines represents a display screen or portion thereof and forms no part of the claimed design. The remaining dashed broken lines illustrating portions of the graphical user interface form no part of the claimed design.

The appearance of the transitional graphical user interface sequentially transitions between the images shown in FIGS. 1-3 or FIGS. 4-6 . The process or period in which one image transitions to another image forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 